Method and apparatus for drying material



A rqm, 1937.

J. B. VOSKAMP METHOD AND APPARATUS FOR DRYING MATERIAD Filed June 29, 934

' IB IVENTOR Patented Apr. 4 13, 1937 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR. name MATERIAL John B. Voskamp, Pittsburgh, Pa. Application June 29, 1934, Serial No. 733,025

18 Claims.

This invention relates to a novel method and apparatus for artificially drying grasses, alfalfa, legumes, and other organic and inorganic materials which are preserved by the removal of moisture therefrom.

Qne object of this invention is to provide a method and apparatus for rapidly removing the moisture from grasses, legumes, and other materials, without physical or chemical decomposi- 10 tion of the material itself during such drying..

Another object is to provide a method and apparatus for thispurpose by the use of which materials of varying densities and moisture contents can be dried at one and the same time and in which the time of drying is controlled entirely by the density of the material.

A further object is to provide a method and apparatus for artificially drying materials. by subjecting them to relatively high temperatures without case hardening the material and with little or no oxidation thereof at these temperatures.

A still further object is to provide a methodfor drying granulated material in which the.

0 material is preheated in a highly humid atmosphere, then delivered directly into a current of drying medium of gradually reducing temperature and velocity, at a. point where the velocity of the current is suflicient to hold the lighter particles thereof in suspension while permitting the heavier particles to seek the higher velocity portion of said current and then holding the material progressively in the areas of reduced velocity for a sufiicient period of time to eventually absorb all the moisture therefrom,

' A still further object is to provide a vertical drying machine in which means are provided for automatically varying the velocity of a current of drying medium in the direction of-travel 40 whereby materials of different densities may be separated and readily dried therein at the same time. I

A still further object of this invention is to provide a method and apparatus for drying grasses, legumes, and otherorganic and inorganic materials in which the materials being,

'driedare subjected to a drying medium of grad- .u'ally reduced velocities and temperatures whereby the material will automatically select the pro er temperature zone for its density and state of dryness. 1 j

A still further object is to produce a novel '--methodand apparatus for drying materials by which the material to be dried is held in direct contact with a current of drying medium of gradually decreasing temperatures and velocities which, not only holds the material in suspension, but also carri the material with it, as the moisture is remove therefrom, whereby the drying material automatically seeks the zones of lower temperatures and lower velocities.

In carrying out my process, I propose to use a vertical tower composed of a series of connected chambers of different diameters which are mounted one above the other with the chamber of smallest diameter at the bottom. The drying medium is introduced into the chamber of smallest diameter and passes upwardlythrough the connected chambers and since each of these chambers is of larger diameter than the chamber immediately subjacent thereto, the velocity of the medium decreases in the next of the connected chambers, but as the passages between these cylinders are restricted to a diameter smaller than either adjacent cylinder, the velocity is increased at these points preventing material from settling back.

The drying medium is preferably introduced into the tower at a somewhat higher temperature than would cause dry material of the kind being dried, to ignite, if introduced into such medium in an atmosphere which would support combustion and the material in a granulated or chopped state is preferably first introduced into direct contact with the medium at a point where its velocity is such that ,the lighter particles thereof tend to be held in suspension in the current of such medium while the heavier particles thereof drop or settle to a lower level in the tower into an area or zone in which the velocity and temperature of the medium are considerably greater than at the point of introduction of the material. As the material comes in contact with the gases, the free moisture therein is extractedtherefrom and absorbed by the drying medium, forming a superheated steam which materially lowers the temperature of the medium, and as the material dries, it becomes lighter in weight or less dense and seeks a new level in the tower where it is again "held in suspension by the reduced velocity of the current in-ja zone of lower temperature until completely dry. 7

In order to give a complete understanding of my invention, I have illustrated one embodiment thereof which is described in the following specification and illustrated in the accompanying drawing, wherein:

Figure 1 is a view in side elevation of a drying machine made in accordance with my invention; Fig. 2 is a top plan view of themachine, and

Fig. 3 is aview in vertical section taken on lines III-III of Fig. 2.

The embodiment of the drying apparatus 11- lustrated in the drawing comprises a vertical tower l which is formed of a series of superimposed cylinders la, lb, lc,,and Id, (each of which is of slightly larger diameter than thesubjacent cylinder), connected together, to form a series of connected airtight chambers by inclined surfaces 2a, 2b, and 2c, the diameters of which at their smallest points are less than the diameters of. the subjacent cylinders.

The upper end of the tower l projects into a concentric cylinder 3which is supported on the tower in any suitable manner, and is provided with an inverted conical partition wall 4 having a pipe 5 extending therefrom which opens into the tower l. The upper end of the cylinder 3 is covered by a plate 8 carrying a downwardly extending pipe 1. This plate 6 and the partition wall 4 forms a cyclone chamber 8 in the cylinder 3 in which the material to be dried and the gases contained therein are separated, the gases passing out through the pipe 1 and the material passing through the pipe 5 into the tower I.

The material to be dried is charged into the chamber in a chopped or granulated state through a charging'valve' 9 connected to a fan l0 which forces the material into a pipe or duct ll leading into the top of the cyclone chamber 8. The upper end of the pipe H is tangentially connected to the cylinder 3 so that the material delivered into the cyclone chamber will be spun by centrifugal force over the partition wall 4 and so difiused as to be readily separated from the conveying gases. The pipe 5 is telescopically contained within a lower pipe l2 which terminates adjacent the top of the cylinder lb and the material in the cyclone chamber 8 is, therefore, delivered directly into the lower part of the tower l'into direct contactwith a current of a 8 suitable non-oxidizing drying medium such as furnace gases, which is delivered to the tower through a duct l3 connecting the chamber la with a suitable furnace, boiler, or other type of heater.

In order to preheat the material being fed into the cyclone chamber and to dilute the oxygen atmosphere contained in the material and thus eliminate or, to a great extent, minimize oxidation which would occur if oxygen containing material was introduced directly into such high temperature gases, the spent gases of the drying 5by cone-shaped members l8.l8a and llib which act to increase the velocity of the current of drying medium as it passes the edges thereof.

The members l6, Ilia, I61 which are reciprocably mounted within the tower 'l toyary the position 7 within said chambers at which such velocity increase is efiective, are carried by a rod ll'and the pipe l2 which is supported ona spider l8 secured to the rod H. at its upper end to a crosshead l9 carried on side 7 rods 20 which are slidably mounted in upper and The rod I1 is connected" lower. brackets 2| and 2la secured to the sides of the cylinder 3.

To periodically reciprocate the rod l1 and thus raise and lower cones l6-l6al6b, the side rods 28 are connected to one end of cables 22 which pass. over pulleys 23 and have their other ends connected to continuously driven cranks 24 which are mounted on a shaft 25 that is continuously driven at the desired speed, in any suitable manner (not shown).

In practice, the wet material is charged into the machine in a chopped or granulated state through the charging valve 9 from which it is delivered to the fan Ill. Here, it is diffused into the spent gases of the drying medium which are being withdrawn from the tower I through the communicating ducts l4 and I5 which are of relatively low temperature and high humidity and as the material comes in contact therewith, it is preheated and is carried thereby into the cyclone chamber 8 through the pipe ll. As the material enters the chamber 8 it is spun by centrifugal force, and passes in a spiral path over the heated partition plate 4 where it receives additional preheating and is separated from the spent gases which are withdrawn through the pipe I.

The preheated material then drops through the communicating pipes 5 and I2 into the chamber lb of the tower l where it is struck by an uptravcling current of drying medium entering the tower through the conduit l3 and passing upwardly therethrough at a relatively high velocity out under a pressure somewhat less than atmosphere as a result of its being drawn therethrough by the suction of the fan It. The material comng in contact with the drying medium is diffused by the high velocity of the current and is held in suspension thereby or moves upwardly ith the, current and any material which is not supported in this velocity or any material dropping back due to interruption of the drying procoss is discharged through a rotary discharge valve 25 connected to the bottom of the chamber la.

As the free moisture is extracted from the material by its contact with the current of drying medium, it is transformed immediately intosuperheated steam and as a result, there is rapid temperature drop in the medium and a part of the drying agent becomes superheated steam, which eliminates any possibility of combustion or oxidization of the drying material.

When the material is diffused in the chamber lb the lighter or less dense material rapidly rises out of the zone of high temperature and seeks avelocity where it cannot rise until it loses sufficient moisture to rise further. As these higher zones are of lower temperature due to the rapid temperature drop bythe formation of steam and as the gases contain a high percentage of superheated steam, the lighter material is progressively subjected to less severe drying conditions. Thus, by this selective process, the heavy or dense wet material seeks and remains longer in the lower zones where it is. subjected to severe drying conditions. 4

Since each of the chambers lb, lo, and Id, is of greater diameter than the chamber immediately subjacent thereto, it is apparent that as the current of drying medium passes upwardly through the tower l, zones of progressively decreasing velocities and lower temperatures will be formed in which the travel of the material is checked or held back and given time to dry. And since the efiective diameter of each of the inclined connecting surfaces 2b, 2c, and the smaller opening ity of the drying medium increases somewhat as it passes upwardly from one chamber to another and then decreases as the gases expand in the next chamber of larger diameter. This increase in the velocity of the gases between. adjacent chambers in effect forms a pneumatic lockand prevents the partially dried material which has such density that it can almost be held in suspension in the drying medium in that chamber from dropping or falling back into a lower chamber where the velocity is higher.

As the material in each of the chambers Ib, lo, and Id of the tower l gives up its moisture, and consequently becomes lighter in weight, it is ad'- vanced into the next higher chamber by the action of the cones I6, Ilia, and IGb which are continuously reciprocated to vary the areas of the chambers successively throughout substantially the full length thereof. Since the velocityof the medium passing through each of the chambers is highest adjacent the cone mounted therein and since the cone is continuously reciprocating, it is apparent that the velocity of the gases is varied successively throughout the' length of the chamber and the material is lifted into the next chamber. The areas of the cones are such with respect to the chambers in which 'they reciprocate that the increased velocity secured adjacent the cones is substantially equal to the velocity of the medium at th'entra'nce to the chamber immediately thereabove, consequently material in any chamber having reached such a state of drynessthat it is capable of being suspended by the oveloc ity of the gases passing around the cones, is not only raised or lifted to the next higher chamber but is prevented from dropping back into a lower chamber by the increased velocities occasioned at the entrance to each chamber.

In order to regulate and control the length of 4 time the material .is held in suspension in the gases in the tower, a shell 26 having a flared portion 21 which cooperates with the partition wall 4 to provide a discharge opening for the gases of the drying medium is adjustably mounted on the cylinder Id. Theshe1l'26.has a cam surface 23' on its lower end which is supported on stationary rollers 29 carried by cylinder Id. Thus by manually turning shell 28 the size of the opening between the bottom of the partition wall 4 and the top of member 21 may be readily varied and controlled to regulate the velocity of the current of drying medium as it leaves the tower I and thus acheck on the dryness of the material before it leaves the drying tower is'obtained. 3 The member 25 may be turned to effect the desired adjustment by anysuitable means (none shown) such as, for example, by a cable looped around the shell and having its ends extending through openings in the 'side of 'themember' 3 where they may be grasped by the operator,

When the material has been thoroughly dried,

it is carried over the flared portion of the shell 26 and drops downwardly into the lower end of the cylinder 3. To separate the spent gases from the dried material, a skirt 30 is. secured to the underside of the partition-wall 4 which divides the lower portion of the cylinder 3 into two chambers 3i and 32 which are in communica-.

tion at the lower end of the skirt.

The material passing overthe shell 26 drops by gravity through the chamber 3| and into a spirally shaped conveyor 33 which delivers the material to a discharge valve 34. As the mateone branch of which leads to a chamber 38 surrounding the chamber lb while the other is open to atmosphere.-- These inert or spentgases delivered to the chamber 38 pass downwardl-y over the outer surtace oi the cylinder Ib absorbing the heat conveyed through the wall of said cylinder, and then pass through ports 39 in the bottom of the cylinder Ib and dilute the current of drying mediumentering thechaniber Ib, thus'materially reducing the temperature thereof. The amount of gas delivered to the chamber I]: through the duct 31 is regulated by a swinging valve 40 which controls the amount of gases passing through the two prongs of the ducts.

While in the-embodiment shown in the drawing the pipe'35 leading to the fan or blower 36 is shown-connected tothe pipe I5, it is to. be

understood that this pipe may. if desired, extend to and be in communication with any other pipe or portion of the tower where spent gases are" conveniently available; Thus, the.pipe 35 might be connected to an extension of the pipe "I and the gases used to convey the material into the chamber 8 would then be introduced into the tower I :to temper the furnace gases.

The reintroduction of the 'gases passing through-the pipe I-into the tower I might be highlydesirable, where the material-being dried gives oil an excessive quantity of dust, since the wet material would-act as a filter and remove substantially all the dust therefrom that might be objectionable if reintroduced into the tower.

- Thus it is apparent that. the machine has sev-' eral readily operable controls and the drying medium in the tower I. may be easily maintained at the proper temperature for drying any kind :of wet material by regulating the amount of fuel burned and by regulating the amount of spent or inert gas. introduced into the chamber Ila-through the duct 31. Further, the final'dryness of the material may also be readily controlled by regulating the velocity of the cur-' rent of drying medium passing upwardly through the tower I and by controlling the final partition wall 4.

From the foregoing description it is apparent 10 forces this gas into-a forked duct or pipe 31,

that in dryinggreen materials "in accordance with my invention, the material is subjectedto four distinct phases of drying in an airtight compartment. In the first'stage the material;- =in its" green or wet state, issubjected to an atmosphere of relatively low temperature and high humidity under a greater than atmospheric pressure for the purpose of,.preheating the pore structure of the material to prevent case hardening thereof when the material comes in di-' rect contact with the current of] high temperature drying medium and to reduce or eliminate any atmospheric oxygen which may be contained in the material and thus minimize the it to the surface and the atmospheric oxygen contained therein is further eliminated.

In the third stage, the material is subjected directly to relatively inert furnace gases of relatively high temperatures which are passing upwardly through the drying tower under a reduced pressure, that is, under the suction of the fan l0. Here, the material is diffused and held for controlled intervals of timein zones of the gases of progressively reduced temperatures and velocities, depending upon its density and moisture content, the heavier portions seeking the areas of highest temperature and the lighter and drier materials seeking the areas of lower temperature where the gases have been tempered by the moisture absorbed from the heavier and wetter particles, and where the drying medium is a mixture of. the flue gas and superheated steam formed from the moisture thus removed. As the free moisture is transformed into superheated steam, the material rapidly loses'its moisture and weight, and is immediately advanced into the areas of lower temperature containing a high percentage of superheated steam, whereby any physical or chemical change in the material itself is eliminated. The material is then held in this medium under lower than atmosphere pressure until it reaches a weight or state of dryness controllable by the operator.

After the material has been dried, it is separated from the drying medium under a reduced pressure, ina temperature well above the dew point and ina heated chamber which is free from oxygen and of gradually reduced temperature. The material is discharged from this chamber in adry state and at a low temperature into the outside air.

It is further apparent that throughout the process the material'itself never reaches a detrimental heat due to the cooking effect of moisture evaporation in the material itseh and to its rapid movement in the high temperature zone. Once dry the material rapidly passes out of the zone where it could absorb heat and is held sufficiently long at low temperature to discharge any moisture bearinggas which mightbe incorporated therein. These spent gases after being separated from the dry material, are then utilized in the initial preheating of the material and aportion of these spent gases are re-introduced into the tower and used to control the temperature of f the drying medium.

It is also apparent from the foregoing description that the material never comes in contact with any rapidly moving parts, such as a fan, except when it is ina wet state, thus shattering of those parts of the material, such as leaves, etc.,

is substantially eliminated.

While I have illustrated one embodiment of my invention, it will be understood by those skilled in the art that certain changes, modifications,

tively high temperature through a series of connected chambers of progressively increased diameters, introducing granulated material into an intermediate chamber where the velocity of the current is sufllcient to hold the lighter particles of the material in suspension therein while permitting the heavier particles to settle into a lower and smaller diametered chamber, progressively increasing the velocities of the gases in each of such chambers to move the heavier material therein into the super-adjacent chamber, and

then withdrawing the dried material from the largest of said chambers.

2. A vertical drying apparatus comprising a vertical tower composed-of a series of superimposed and communicating chambers, each chamber being of greater diameter than the subjacent chamber, means for introducing a current of drying medium into the lower end of said tower,

means'for delivering granulated material direct-' 1y into the smallest of said chambers, and means within said tower for restricting the area of successive sections of each of said chambers.

3. A drier comprising a vertical tower composed of a series of superimposed and communicating chambers, each successive chamber from locity of the current entering such chambers, a

reciprocable area restricting member in each of said chambers, and means for reciprocating, said area restricting members.

4. An apparatus of the character described comprising a vertical tower having successive sections of larger diameter than the subjacent sections, means within said tower for partially restricting the area of a section of said tower, means for reciprocating said area restricting means, means for delivering granulated material to the bottom of said tower and means for passing a current of drying medium upwardly through said tower.

5. An apparatus of 'the character described comprising a vertical tower, a reciprocable member within said tower, means for passing a current of drying medium upwardly through said tower, means for delivering material to the lower end of said tower intodirect contact with said current, said tower including means for reducing the velocity of the current in the direction of travel, and means forreciprocating said member to alter the velocity of the current at successive sections in said tower.

6. An apparatus of the character described comprising'in combination, a vertical tower having a series 01' chambers of. increased diameters. means for supplying said tower with a drying medium, means for passing said medium in a current'upwardly through said tower under less than atmospheric pressure and for withdrawing it therefrom, means for utilizing a'portion-of the spent drying medium withdrawn from said tower for preheating the material to be dried, means for separating said material from such spent gases, means for delivering the separated material directly into the bottom of said tower, and means for introducing" spent gases in the current of dry-- ing medium to control the temperature thereof. "7. An apparatus for drying materials, comprising a series of superimposed and connected cylindrical members, each of which is of increased diameter over the cylinder immediately subjacent thereto, a separator supported on the top of said cylinders, means for creating an uptraveling current of a drying medium in said connected cylinders, means for withdrawing a portionbf the gases from said tower and utilizing the same to preheat and convey material into said separator, means associated with said separator for delivering the material into direct contact with the current of drying medium,-reciprocating means for holding the material for predetermined intervals in each of said chambers, and means for introducing spent gases into said current to regulate the temperature thereof.

8. In an apparatus of the character described comprising a vertical tower, a cylindrical member supported on said tower and having a sloped surface spaced above the top of said tower, and

means for regulating the size of the opening between the top of said tower and the bottom of said sloped surface.

9. In an apparatus of the character described comprising a vertical tower, a cylindrical member supported on said tower and having a sloped surface extending into and spaced from the top of said tower, and a member supported on said tower and movable relative thereto for varying the size of the opening between the top of said tower and the bottom of said slopedsurface.

10. An apparatus for drying materials comprising a vertical tower having a series of connected chambers of progressively increased diameters, a separator supported on said tower and having a sloped surface spaced from the top of said tower,

means for introducing gases of a drying medium into the lower end of said tower, a suction fan for drawing such gases upwardly through said tower and for utilizing the gases withdrawn therefrom for delivering material to said separator, means associated with the separator for introducing the material into the current of gases, means for regulating the velocity of the gases at the top of the tower to control the discharge of the material therefrom, and means for re-introducing a portion of the spent gases into said tower to regulate the temperature of the drying medium.

11. The method of drying shredded materials which consists in establishing an uptraveling current of drying medium, maintaining zones of successively decreased velocities at regulauspaced intervals along the course of travel of said ourrent, introducing shredded material into an intermediate velocity zone in said current and allowing it to seek a zone in which, it is capable of being held in suspension therein, and moving the partially dried-material from a higher velocity zone intoa lower velocity zone, by varying the velocity of thecurrent in each of said zones.

12. Apparatus for drying materials comprising a series of connected cylinders forming a vertical tower, each of said cylinders being greater in diameter than the cylinder immediately subjacent thereto, means for inducing a current of drying medium upwardly through said tower, means at the entrance to each cylinder for increasing the velocity of the current, means within each of said cylinders for progressively varying the velocity of the current at successive sections along the length of each of said cylinders, and means for introducing shredded material into said tower into direct contact with the current of drying medium.

13. The method of drying wet material which consists in inducing an uptraveling current of drying medium in a tower composed of a series of superimposed chambers, each of which is of greater diameter-than the chamber immediately subjacent thereto to provide successive zones in said current of progressively decreasing velocities, maintaining the current at the entrance to each chamber at a higher velocity than thevelocity in the subjacent chamber, introducing wet shredded material into said current at its point of highest velocity and varying the velocityof the current at successive sections throughout the major portion of the length of each chamber to move the material therein into the next superadjacent chamber.

14. The method of drying materials which consists in passing a current of gases of relatively high temperature through a series of connected chambers of progressively increased diameters, introducing granulated material into such current and permitting the material to seek a velocity of the current capable of holding the particles current in either of the adjacent chambers to prevent the partially dried material from dropping back into a lower chamber and then with-- of the material in suspension therein in the sev- I drawing the dried material from the largest of said chambers.

15. Apparatus for drying granulated material comprising a series, of superimposed cylinders forming a vertical tower, each of said cylinders being of greater diameter than the cylinder immediately subjacent thereto and having an orifice at the bottom of less diameter'than the diameter of the subjacent cylinder, an area restricting member reciprocably mounted in each of said cylinders, means for periodically reciprocatingsaid members, means for inducing an uptraveling "current of drying medium through said tower, and means for introducing shredded material into said tower 'into direct contact with the drying medium.

16. An apparatus for drying materials comprising a series of superimposed and communicating cylinders forming a tower, each of which isof greater diameter than the cylinder immediately subjacent thereto, a separator supported on the top of said connected cylinders, means for creating an uptravelling current of drying medium through said tower, means for varying the space between said separat'or'and the top of said tower to regulate the velocity of the uptravelling current, means for withdrawing a portion of the gases from said tower and utilizing the same to preheat and convey material into said separator, means for delivering the material in said separator directly into the current of drying medium in said tower, reciprocable means in each of said chambers, and means for periodically reciprocatcreating an uptraveling current of drying medium through said tower, means for varying the space between said separator and the top of saidtower to regulate the velocity of the current leaving 10 members.

said tower, means for withdrawing 'a portion of the gases from said tower and utilizing the same to preheat and convey the material into said separator, an area restricting member at the entrance to each of said cylinders for increasing the velocity of the current of 'drying medium as it passes from one cylinder to another, a movable area restricting member in each of said cylinders and means for reciprocating said area restricting 18. An apparatus of the character described comprising a vertical tower having a series of successively enlarged chambers from the bottom to the top, means for creating an uptraveling 'current of drying meditnn through said tower, 

